import sys, math
sys.setrecursionlimit(10**7)
from itertools import *
from heapq import heapify, heappush, heappop
from collections import deque, defaultdict, Counter
from bisect import bisect_left, bisect_right
from copy import copy, deepcopy
# from sortedcontainers import SortedSet, SortedList, SortedDict
INF, LINF, ipt = float('inf'), 1 << 60, sys.stdin.readline
iin, mii = lambda: int(ipt()), lambda: map(int, ipt().split())
lmi = lambda: list(map(int, ipt().split()))

Q, Y = mii()
s = input().split()

def solve(x):
    """f(x) >= Y"""
    st = deque()
    for i in range(Q):
        if s[i].isdigit():
            st.append(int(s[i]))
        elif s[i] == "X":
            st.append(x)
        elif s[i] == "+":
            a = st.pop()
            b = st.pop()
            st.append(a + b)
        elif s[i] == "min":
            a = st.pop()
            b = st.pop()
            st.append(min(a, b))
        elif s[i] == "max":
            a = st.pop()
            b = st.pop()
            st.append(max(a, b))
    
    return st.pop()

ok = 10**13 + 10
ng = -1

while ok - ng > 1:
    mid = (ok + ng) // 2
    if solve(mid) >= Y:
        ok = mid
    else:
        ng = mid

if solve(ok) == Y:
    print(ok)
else:
    print(-1)